ABB and Alstom Grid hybrid HVDC circuit breakers

I have written before about ABB's HVDC hybrid breaker and its meaning, and about the reasons that breakers that are more economical than their breaker (or Alstom Grid's competitive design) are needed to enable a cost effective supergrid. This post focuses more on the steps needed to enable the eventual supergrid; by that, I refer to the "mesogrid" voltage levels in a future DC grid.